11C-carbon dioxide fixation and equilibration in rat brain: effects on acid-base measurements.
The positron-emitting isotope 11C was used to label CO2 for studies of metabolic fixation and equilibration after a single-breath inhalation by rats. Metabolic fixation and loss of the label via exhalation caused the metabolized fraction of the label in the brain to rise to 30.1 +/- 0.7% within 30 minutes. The T12 for equilibration of the label between blood and brain was 1.95 minutes. When the label was 95% equilibrated, 12% was metabolically trapped by brain, and when only 5% was trapped, the blood-brain equilibration process was only 50% complete. Labeled CO2 thus has limited usefulness as an acid-base or metabolic tracer for positron-emission tomography.
D000136:Acid-Base Equilibrium; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D006207:Half-Life; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D014055:Tomography, Emission-Computed
D002245:Carbon Dioxide